1. Field of the Invention
The present invention relates to a backgauge device, and more specifically, it relates to a backgauge device on a working device such as a shearing machine or press brake and the like, which processes a workpiece of metal plate.
2. Description of the Prior Art
For example, in a shearing machine or press brake or the like, in order to accurately carry out the positioning of a metal plate work piece relative to the working position at which the work is processed by means of upper and lower processing tools, a backgauge device is usually provided which is freely movable in the forward and backward directions with reference to the working position. In the conventional backgauge device there is a pair of guide members which are separated from each other in the left and right direction and extending in the forward and backward directions. On each of these guide members are respectively supported movable members which are freely movable in the forward and backward direction. A beam member, which supports a plurality of work stoppers extending in the left and right direction in order to carry out the predetermined positioning of the workpiece, is fixed near the opposite ends thereof on the previously mentioned movable bodies. In addition, in order to move each movable member in the forward and backward direction along each guide member, right and left ball screws are provided contiguous to each guide member and parallel to the guide members, and a ball nut which is threadably fitted to each ball screw is connected integrally to each of the previously mentioned movable bodies. Furthermore, in order to drive the ball screw rotationally, a servomotor is connected to one ball screw, and the left and right ball screws rotate synchronously, and the left and right ball screws are connectively linked through a gear mechanism or a chain mechanism.
Accordingly, since a plurality of ball screws are rotated by means of one servo-motor, a comparatively large servo-motor is required, and the overall construction is very sturdy and complicated, which is a problem in the prior art working apparatus.
In addition, the left and right movable bodies which are located near the opposite edges of the beam member are capable, by synchronous rotation of the ball screw, of moving simultaneously in the forward and backward directions. For and this reason, it is usually necessary to move the left and right movable bodies while maintaining a uniform and accurate attitude so as not to exert any bending action or unreasonable external force on the supporting section of the beam. Accordingly, the mounted section of the guide member which guides and supports the left and right movable bodies must be processed in a highly precise manner, which is also a problem in the prior art working apparatus.